Chip packages with sintered interconnects formed out of pads

ABSTRACT

The present invention is directed to a method for interconnecting two components. The first component includes a first substrate and a set of structured metal pads arranged on a main surface. Each of the pads includes one or more channels, extending in-plane with an average plane of the pad, so as to form at least two raised structures. The second interconnect component includes a second substrate and a set of metal pillars arranged on a main surface. The structured metal pads are bonded to a respective, opposite one of the metal pillars, using metal paste. The paste is sintered to form porous metal joints at the level of the channels. Metal interconnects are obtained between the substrates. During the bonding, the metal paste is sintered by exposing the structured metal pads and metal pillars to a reducing agent. The channels and raised structures improve the penetration of the reducing agent.

BACKGROUND

The present invention relates in general to the field of microelectronicpackages, components thereof and methods to bond such components andobtain such packages. In particular, the present invention relates totechniques to obtain metal interconnects based on metal pads (e.g.,copper pads) structured to ease the penetration of the reducing agent.

Various bonding processes are known, which involve solders, such as theso-called mass-reflow solder, copper-pillar solder reflow andcopper-pillar compression techniques. Such techniques allow a range ofinterconnect pitches to be obtained (namely from 20 to 130 μm), withdifferent qualities of interconnects.

The above techniques all involve an isothermal sintering step to bindopposite components of the package. It has also been proposed to applycopper-paste on copper pillars of one of these components, in order tobind the components by sintering. Formic acid enriched nitrogen istypically used as a reducing agent to remove the copper oxide formedduring the material fabrication and handling during the bonding process.Other reducing agents, such as formic gas can be used as well. Thismakes it possible to obtain a satisfactory electrical conduction throughthe interconnects.

SUMMARY

According to a first aspect, the present invention is embodied as aninterconnect component. The latter comprises a substrate and a set ofstructured metal pads arranged on a main surface of the substrate. Thepads are designed for fabricating metal interconnects with respectivemetal pillars on an opposite substrate. Each of the structured metalpads comprises one or more channels. Each of the channels extendsin-plane with the average plane of their respective pads, so as to format least two raised structures thereon.

According to another aspect, the present invention is embodied as a setincluding a first interconnect component, such as described above. Theset further comprises a second interconnect component, which includes asecond substrate and a set of metal pillars arranged on a main surfacethereof. The pads of the first components are adapted for fabricatingmetal interconnects with respective metal pillars on the secondsubstrate. The second interconnect component may for instance compriseelectronic components in electrical communication with at least some ofthe metal pillars.

The two components may be provided separately, or together but in anon-assembled state. However, in embodiments, the structured metal padsof the first component are bonded to respective, opposite metal pillarsof the second component, due to metal paste, (e.g., so as to form amicroelectronic package). The paste is sintered; it forms porous metaljoint(s) at the level of the channel(s), so as for the pads and pillarsto form metal interconnects between the first and second substrates.

According to a final aspect, the present invention is embodied as amethod for interconnecting two interconnect components such as describedabove. This method relies on bonding each of the structured metal padsto a respective, opposite one of the metal pillars, due to metal paste.As said above, the paste is sintered so as to form porous metal joint(s)at the level of the channel(s), in order to obtain metal interconnectsbetween the first and second substrates. During the bonding, the metalpaste is sintered and the structured metal pads and metal pillars areexposed to a reduction agent or reaction product(s) thereof.

Devices methods embodying the present invention will now be described,by way of non-limiting examples, and in reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These and other objects, features and advantages of the presentinvention will become apparent from the following detailed descriptionof illustrative embodiments thereof, which is to be read in connectionwith the accompanying drawings. The various features of the drawings arenot to scale as the illustrations are for clarity in facilitating oneskilled in the art in understanding the invention in conjunction withthe detailed description. In the drawings:

FIG. 1 is a 2D cross-sectional view of a set of interconnect components,before assembly (pads and pillars are not bonded yet), as inembodiments;

FIG. 2 shows a (wider) 2D cross-sectional view of the same components,after assembly, wherein pads and pillars are bonded thanks to a metalpaste, so as to form a chip package wherein two substrate areinterconnected, according to embodiments;

FIGS. 3A-3E show various metal pads, structured so as to comprisein-plane channels, as involved in embodiments;

FIGS. 4A-4D is a sequence of 2D cross-sectional views illustratinghigh-level fabrication steps of a chip package, according toembodiments; and

FIGS. 5 and 6 are 2D cross-sectional views focusing on a singleinterconnect of a device similar to that of FIG. 2, according toembodiments.

The accompanying drawings show simplified representations of devices orparts thereof, as involved in embodiments. Technical features depictedin the drawings are not necessarily to scale. Similar or functionallysimilar elements in the figures have been allocated the same numeralreferences, unless otherwise indicated.

DETAILED DESCRIPTION

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it can be understood that the disclosed embodiments aremerely illustrative of the claimed structures and methods that may beembodied in various forms. This invention may, however, be embodied inmany different forms and should not be construed as limited to theexemplary embodiments set forth herein. In the description, details ofwell-known features and techniques may be omitted to avoid unnecessarilyobscuring the presented embodiments.

References in the specification to “one embodiment”, “an embodiment”,“an example embodiment”, etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

For purposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the disclosed structures andmethods, as oriented in the drawing figures. The terms “overlying”,“atop”, “on top”, “positioned on” or “positioned atop” mean that a firstelement, such as a first structure, is present on a second element, suchas a second structure, wherein intervening elements, such as aninterface structure may be present between the first element and thesecond element. The term “direct contact” means that a first element,such as a first structure, and a second element, such as a secondstructure, are connected without any intermediary conducting, insulatingor semiconductor layers at the interface of the two elements.

Referring to FIGS. 4A-4D, an aspect of the present invention is firstdescribed, which concerns a method for interconnecting two components11, 12 of, e.g., a chip package.

As seen in FIG. 1, the first interconnect component 11 comprises asubstrate 111, as well as a set of structured metal pads 114 that arearranged on a main surface of this substrate 111. Each of the structuredmetal pads 114 comprises one or more channels 116. Any such channelextends in-plane with (i.e., parallel to) the average plane of itsrespective pad 114, so as to form at least two raised structures 115thereon. The metal pads 114 are typically patterned during a previousstep (e.g., using electroplating methods, not shown), so as obtain thedesired channels 116 and raised structures 115.

As further seen in FIG. 1, the second interconnect component 12 toocomprises a substrate 121. This component 12 further includes a set ofmetal pillars 124 arranged on a main surface of the substrate 121.

The manufacturer may provide any or each of these components 11, 12separately from the other, or together but in a non-assembled state.However, in variants as specifically contemplated in the presentmethods, each of the structured metal pads 114 of the first component 11may be bonded S20-S40 to a respective, opposite metal pillar 124 of thesecond component, using metal paste 22, 22 a, in order to interconnectthe components 11, 12. The metal paste is sintered so as to form porousmetal joints 118 at the level of the channels 116.

During the bonding step S40, the metal paste 22, 22 a is sintered whileexposing the structured metal pads 114 and metal pillars 124 to areduction agent or one or more reaction products thereof. This makes itpossible to obtain electrically conductive metal interconnects 134between the first substrate 111 and the second substrate 121.

In preferred embodiments, the structured metal pads 114 are applied S40with bonding pressure to the respective, opposite metal pillars 124, assuggested in FIG. 4D. Reasons for doing so are discussed below indetail.

Various reduction agents can be contemplated, starting with formic acid.Preferably though, the concentration of formic acid vapor is controlled,during the bonding step, by mixing the formic acid vapor with a gas suchas nitrogen. The latter is used as carrier gas and it does notparticipate in the reduction chemical reactions. Reaction by-products,such as carbon monoxide and hydrogen gas, may happen to be recirculatedand hence further participate in the reduction chemical reactions. Moregenerally, any suitable reducing agent can be contemplated to remove theoxide formed during the material fabrication and handling, so as toobtain satisfactorily conductive interconnects 134.

Preferred embodiments involve a dipping transfer method. In other words,the structured metal pads 114 and/or the metal pillars 124 may be dippedS20-S30 into a metal paste 22 (FIG. 4B), prior to applying S40 thestructured metal pads 114 to respective, opposite metal pillars 124. Tothat aim, the metal paste 22 may for instance be applied S10 on asubstrate 20, using any suitable spreading tool 24. Embodimentsillustrated in FIGS. 4A-4C assume that only the pillars 124 are dippedinto the metal paste 22, resulting in paste residues 22 a adhering onthe lower surface of the pillars (FIG. 4C). According to at least oneother embodiment, only the pads 114 or each of the pads and pillars canbe dipped into metal paste 22. According to yet another embodiment,instead of dipping transfer methods, other methods such as the so-calleddispensing, screen printing or stencil printing methods may be reliedon, as known per se.

The first interconnect component 11, which concerns an independentaspect of the invention, will now be discussed in detail. As seen inFIG. 1, and also in FIGS. 3, 5 and 6, each metal pad 114 includes atleast one in-plane channel 116. Yet, and as seen in FIGS. 3A-3E, thepads may include two or more channels 116. A channel 116 is typicallyformed as a trench, or a groove, extending in-plane with (i.e., parallelto) the average plane of its respective pad 114 and thus parallel to theupper plane of the pad. The channels 116 ideally extend parallel to theaverage plane of the substrate 111, on which the pads 114 are arranged.A channel 116 results in two outer, raised structures 115. The raisedstructures 115 can also be referred to as pedestals. A channel 116 shalltypically have a rectangular section or a rounded section. Yet, sincethe pads 114 are preferably electroplated, the section is typicallyrectangular, as assumed in the accompanying drawings. In variants,etching techniques may be used, which may possibly result in channelswith rounded sections.

The pads 114 are designed to fabricate metal interconnects 134 withrespective metal pillars 124 on an opposite substrate 121, for example,using a dipping transfer method such as described above. The pads 114accordingly form platforms for the metal pillars 124. The pads 114preferably are electroplated copper pads. In variants, aluminum pads maybe contemplated. Similarly, the opposite pillars may include copper oraluminum. Copper is preferred, owing to its very high electricalconductivity. However, in other variants, the interconnects 134 may alsobe formed by sintering from nano- or micro-metal particles. Thus, moregenerally, metal pads and metal pillars are assumed.

Remarkably here, the presence and configuration of the channels 116allows an improved penetration of the reducing agent during thesintering process. This, eventually, results in improved metalinterconnects 134, which may possibly be arranged with a small pitchwhile having satisfactory electrical properties. The channels 116 helpin the evaporation of the solvent contained in the metallic paste (e.g.,copper paste) used during the bonding process, to obtain theinterconnects 134.

For example, assuming that a copper paste is used, the reduction of thenative copper oxide allows a sintering of the copper paste 22 a to beperformed, typically at a temperature of about 200° C. For example,formic acid enriched nitrogen can be used as a reducing agent, attemperatures above 150° C. Once the copper oxide is reduced, the copperpaste starts immediately to sinter.

A non-complete sintering of the copper joint may occur due to thelimited penetration length of the reducing agent in the metal paste,especially if a bonding pressure is applied, as in preferredembodiments. Therefore, during the sintering process, the periphery ofthe copper joint is rapidly reduced as it starts to sinter. Thisphenomenon happens to close the porosity of the joint and, in turn,hinders the penetration of the reducing gas toward the center of theinterconnect. The limited penetration of the reducing agent limits theeffective area of the metal (e.g., copper) joint 118, 119, which in turnlimits the electrical contact between the pad 114 and the oppositepillar 124. In that respect, the metal paste is typically not conductive(or has a very limited conductivity) before sintering or if notsufficiently reduced. Therefore, channels 116 may advantageously beprovided on the pads 114 to improve the penetration of the reducing gasand eventually decrease the resistivity of the obtained interconnect134, at the level of the joints 118, 119.

Applying pressure during the sintering process is desired as this allowsachieving a low porosity region 119 (whose porosity is typically lessthan 20 or 30%). This, in principle, improves performance, compared tointerconnects obtained without applying any pressure. Note, however, theapplied pressure may have little impact on the porosity of the innerjoint 118. Still, applying pressure may be desired to improve thehorizontal joint 119. Note that if the porosity is sufficiently high(e.g., 20% porosity or more), the pores in the metal paste aresufficiently open, which allows a sufficient penetration of the reducinggas. However, when applying pressure, a closed pore joint structure 119typically results which limits the penetration of the reducing agent.This, eventually, impacts the reduction reactions, whence the benefit ofthe channels 116, which can compensate for this as they improve thepenetration of the reducing agent, notwithstanding the applied pressure.

It is therefore of advantage to rely on structured pads 114. Aspects ofthe invention therefore concern a component 11, comprising suchstructured pads 114, as well as a set of components 11, 12, whichfurther includes the counterpart component 12.

In typical embodiments, the opposite substrate 121 (i.e., comprising themetal pillars 124) comprises electronic components and thus make up anintegrated circuit chip. Note that the substrate 111 with pads 114 doesnot necessarily include electronic components. However, thisconfiguration may be reversed (e.g., only the substrate 111 compriseselectronic components) or symmetrized (e.g., electronic components arearranged on both substrates 111, 121). In that case, electroniccomponents would likely be arranged in electrical communication withpart or all of the metal pads 114.

Thus, in general, structured pads 114 may be provided on either side111, 121, or on each side 111, 121. In addition, the thickness (orheight) of the opposite pillars 124 (or of opposite structured pads)need not systematically be larger than that of the pads 114. Forexample, shallow pillars and thick structured pads may be used onrespective sides 111, 121, or have similar heights or, still, structuredpads may be involved on each side 111, 121, which may have similar ordifferent heights, contrary to the assumption made in the accompanyingdrawings.

In this description, the terminologies “structured metal pads” and“metal pillars” respectively may refer to pads and pillars that compriseat least 80% of pure metal (e.g., copper), and preferably more than 90%(or even 95%) of pure metal. As said, the pads are typically made ofcopper. However, the pads may possibly be coated with nickel,nickel/gold, palladium, or palladium/gold, during their preparation.Thus, owing to the possible presence of residues in (on) the pads, thelatter may not necessarily be made of pure metal.

Referring now more specifically to FIGS. 3A-3E, some, or each of thestructured metal pads 114 a-e preferably comprise two or more channels116 a-e, each extending in-plane with the average plane of theirrespective pads. Note that the pads 114 a and 114 b have a structurecompatible with the cross-sections assumed in FIGS. 1, 2 and 5. Two ormore channels form at least three raised structures 115 a-e on a pad 114a-e. More generally, a pad may comprise n channels (n=1, 2, 3, 4, . . .as in FIGS. 3A-3E). The n channels may notably extend parallel to eachother (as in FIGS. 3A, 3C), hence giving rise to n+1 structures, likebars (as in FIG. 3A. Channels may also be transversely arranged, to forman array, as in FIG. 3B. In the latter case, assuming n=n1+n2 channelsare formed, including a first set of n1 parallel channels and a secondset of n2 channels extending, each, transversely to the n1 channels,then typically (n1+1)×(n2+1) raised structures 115 b are formed on thepad. In all cases, the raised structures may form a 1D or 2D pattern ofrepeating structures, possibly identically repeated (as in FIG. 3A, 3Bor 3D), such as to form a regular array (as in FIG. 3A or 3B), or not(FIG. 3D, where the raised structures 115 d are neverthelessrotationally symmetric). More sophisticated arrangements can becontemplated (as in FIG. 3E).

In general, increasing the channels may improve the reduction gaspenetration. However, additional technical considerations may come intoplay. For example, channels 116 a may form a 1D pattern of regularlyspaced parallel bars 115 a (or post), as in FIG. 3A, or a 2D pattern ofrepeating mesas 115 b, as in FIG. 3B. In some embodiments, repeatingbars 115 a may be preferred, where redistribution lines come to contactthe lower pads 114. This is to mitigate (or prevent) possibleelectromigration effects that may arise due to current crowding in thelow porosity copper layer, rather than the high porosity copper layer,as discussed later in reference to FIGS. 5 and 6. More or lesssophisticated variants can be contemplated, as illustrated in FIGS.3B-3E, to improve the gas penetration and optimize the interconnect areaby achieving a low porosity interconnect layer 119.

The pads 114 a-d may notably have a rounded (e.g., cylindrical) shape,as in FIG. 3C, or a cuboid (e.g., parallelepiped) shape, as in FIGS. 3A,3B, 3D, and 3E. The general shape of the pad may have little impact.More important are the channel and structure dimensions. In particular,the raised structures should preferably have dimensions that are smallerthan the critical forming gas penetration length.

In that respect, the average in-plane dimension ws of the raisedstructures 115 is preferably between 4 and 10 μm. In other words, ws∈[4μm; 10 μm]. Preferably though, ws∈[5 μm; 8 μm]. This dimension ismeasured parallel to the average plane of the pad 114. For example, thisdimension corresponds to the average in-plane width of a bar (as in FIG.3A or 3C) or to the average in-plane diameter of a mesa, as in FIG. 3B.

Sufficiently large in-plane dimensions of the raised structures 115 arepreferable (i.e., at least 4 or 5 μm), to improve the low-porositybonding area 119 with opposite pillars 124. However, the in-planedimension of the raised structures is preferably kept below the maximalpenetration length (typically 9 or 10 μm) of the reducing agent, toensure a good lateral penetration of the latter and, in turn, a goodsintering quality. The critical penetration length of formic acid is forinstance estimated to be of approximately 9-10 μm.

In general, an interval of 4 to 10 μm allows a good reduction throughthe raised structure 115 (i.e., where the bonding pressure is typicallyapplied) as the reducing gas can typically penetrate the paste 22 athrough 4 to 10 μm.

Preferably, the average thickness ts (or height) of the raisedstructures 115 is between 2 and 6 μm (ts∈[2 μm; 6 μm]). The thickness(or height) measured perpendicularly to the average plane of the pads114. The thickness ts incidentally corresponds to the depth of theneighboring channels 116. Sufficiently deep channels improve the gaspenetration. Preferably though, the depth ts∈[3 μm; 5 μm].

The average width wc of the channels 116 is preferably between 1 and 6μm (wc∈[1 μm; 6 μm]). The width wc is measured in-plane with the averageplane of the pads 114. This average width corresponds to the in-planegap between two structures 115 separated by a channel. Said width cantypically be as low as 1 μm and still allow a satisfactory gaspenetration. On the other hand, and given the typical in-planedimensions of the pads 114 and pillars 124 (typically a few 10s of μm),it may be necessary to limit the width of the channels, e.g., to 6 μm,so as to ensure reasonably low porosity for the interconnect area. Morepreferably, the average width of the channels is limited to wc∈[2 μm; 5μm].

Owing to the limited in-plane dimensions of the pads and the interplaybetween the dimensions of the channels and raised structures, one maywant to impose altogether all of the above dimensional constraints so asto have wc∈[1 μm; 6 μm] (or even wc∈[2 μm; 5 μm]), ts∈[2 μm; 6 μm] (orpreferably ts∈[3 μm; 5 μm]) and, altogether, ws∈[4 μm; 10 μm] (or evenws∈[5 μm; 8 μm]).

A third aspect of the invention is now briefly described which concernsa set 1 of components, such as depicted in FIG. 1. As already describedearlier, this set 1 includes a first interconnect component 11 (withstructured metal pads 114 arranged thereon) and a second interconnectcomponent 12, with metal pillars 124. As already described earlier, thestructured pads 114 make it possible to obtain improved metalinterconnects 134 with respective metal pillars 124 on the oppositesubstrate 121.

Most preferably, the average in-plane dimension of the pads 114 issubstantially equal to that of the pillars 124 or larger (to cope withmisalignment). Such dimensions are measured parallel to the respectivesubstrates 111, 121, respectively. They may correspond to an averagediameter, assuming cylindrical pads and pillars, or to the averagelength of an edge of the pads and pillars (if the pads and pillars areparallelepiped). In other words, the pads and pillars preferably allhave matching (in-plane) dimensions. In addition, the pillars (andsimilarly the pads) are preferably all identical, subject to fabricationtolerances.

As said, the second interconnect component 12 may comprise electroniccomponents in electrical communication with (at least some of) the metalpillars 124. Now, such electrical components may in fact be provided onthe first substrate 111 only or on both substrates 11, 12. In the designoption assumed in the accompanying drawings, the substrate 12 (e.g., achip) comprises electrical contacts 122 (e.g., electrical lines ortraces), in electrical contact with the pillars 124. Such contacts 122may connect pillars 124 to each other, and/or may connect electricalcomponents of the chip 12 to the pillars 124, as usual in the art.

As noted earlier too, the interconnect components 11, 12 of the set 1may be provided separately by the manufacturer. They may further beprovided altogether, but in a non-assembled state (not yetinterconnected), as depicted in FIG. 1. A manufacturer may furtherprovide only one of these components 11, 12.

Once interconnected (e.g., using the present methods), the above setforms a set 2, 2 a of interconnected components 11, 12, such as depictedin FIG. 2, 5 or 6, giving rise to interconnection areas 118, 118 a, 119(sintered metal paste 22 a). Such interconnected components 11, 12 maynotably be involved in chip packages of integrated circuits and compriseprinted circuit boards, as usual in the art.

Referring to FIG. 2, 5, 6, once assembled and interconnected, the set 2,2 a comprises structured metal pads 114 (e.g., copper pads) that are,each, bonded to a respective, opposite one of the metal (e.g., copper)pillars 124, due to metal paste 22 a. As explained earlier, the laterhas been sintered so as to form porous metal joints 118, 118 a at thelevel of the channels 116. As a result, the pads 114 and oppositepillars 124 form metal interconnects 134 between the substrates 111,121.

As also noted earlier, a thin layer 119 of sintered metal (e.g., copper)paste typically remains in the middle (i.e., in the intermediate regionbetween the raised portions 115 of the pads 114 and the opposite pillars124). Thus, after bonding (sintering), the joints 118, 118 a are partlyporous (typically 20-30% porous) in the trenches. Yet, in theintermediate regions 119 between the pillars 124 and the pedestals 115,the porosity can typically be lower than 20%, depending on whetherpressure was applied or not.

As said, pressure is preferably applied during the sintering. As thetemperature is raised to that aim, a reduction agent is introduced, sothat the porosity of the residual paste 22 a changes. Open porous joint(20-30% porosity) remains in the trenches after sintering, while a lowporous joint is formed at the interface 119. Yet, the interconnects 134may, as a whole, typically be regarded as low porous interconnects,having closed pores after sintering.

Referring now more specifically to FIGS. 5 and 6: in embodiments, thesubstrate 111 comprises redistribution lines 112 formed on and/or in thefirst substrate 111. The lines 112 connect to metal interconnects 134,at the level of respective pads 114. In operation, a redistribution line112 allow electrical current to flow from the line 112 to the connectedinterconnect 134, through a respective pad 114, as depicted by curvedarrows in FIGS. 5 and 6. The redistribution lines 112 may for instancebe formed partly in the substrate 111, or on the latter.

Now, the channels 116 of the pads 114 may be preferably arranged so asfor electrical current to essentially pass through one (or more) of theraised structures 115, as assumed in FIG. 5. More preferably yet,electrical current should essentially pass through a single one of theraised structures 115 (rather than through a porous joint 118 a, as inFIG. 6). Indeed, due to current crowding effects that may occur at thepoints of entrance of the current into the interconnects 134 (especiallyin the low porosity copper region 118, which possibly results inelectromigration effects), the pads 114 are preferably structured andarranged so as for electrical current to essentially pass through asingle raised structure 115, before passing through a low-porosityregion 119, as assumed in FIG. 5. In other words, the design andarrangement of the channels preferably consider the position of entranceof the current.

Now, because of the typical width of redistribution lines 112, it may bepreferred to have electrons entering the interconnect 134 through abar-like structure 115 a (as in FIG. 3A) rather than through a series ofmesas 115 b (as in FIG. 3B), to avoid substantial current densitiesthrough the porous joints 118 formed at interstitial spaces (channels).In all cases, raised structures 115 should preferably be arranged at aperipheral edge of the pad (i.e., at the entrance point of the current).

The methods described herein can be used in the fabrication ofintegrated circuit chips. The resulting integrated circuit chips can bedistributed by the fabricator in raw wafer form (that is, as a singlewafer that has multiple unpackaged chips), as a bare die, or in apackaged form. In the latter case the chip is mounted in a single chippackage (such as a plastic carrier, with leads that are affixed to amotherboard or other higher level carrier) or in a multichip package(such as a ceramic carrier that has either or both surfaceinterconnections or buried interconnections). In any case the chip canthen be integrated with other chips, discrete circuit elements, and/orother signal processing devices as part of either (a) an intermediateproduct, such as a motherboard, or (b) an end product. The end productcan be any product that includes integrated circuit chips, ranging fromlow-end applications to advanced computer products.

While the present invention has been described with reference to alimited number of embodiments, variants and the accompanying drawings,it will be understood by those skilled in the art that various changesmay be made and equivalents may be substituted without departing fromthe scope of the present invention. In particular, a feature(device-like or method-like) recited in a given embodiment, variant orshown in a drawing may be combined with or replace another feature inanother embodiment, variant or drawing, without departing from the scopeof the present invention. Various combinations of the features describedin respect of any of the above embodiments or variants may accordinglybe contemplated, that remain within the scope of the appended claims. Inaddition, many minor modifications may be made to adapt a particularsituation or material to the teachings of the present invention withoutdeparting from its scope. Therefore, it is intended that the presentinvention not be limited to the particular embodiments disclosed, butthat the present invention will include all embodiments falling withinthe scope of the appended claims. In addition, many other variants thanexplicitly touched above can be contemplated. For example, othermaterials than those explicitly mentioned can be contemplated, inparticular for the structured pads and pillars.

What is claimed is:
 1. An interconnect component, comprising: asubstrate; a set of structured metal pads arranged on a main surface ofthe substrate, the pads adapted for fabricating metal interconnects withrespective metal pillars on an opposite substrate, wherein each of thestructured metal pads comprises one or more channels, each extendingin-plane with an average plane of said each of the structured metalpads, so as to form at least two raised structures thereon.
 2. Theinterconnect component of claim 1, wherein each of the structured metalpads comprises two or more channels, each extending in-plane with anaverage plane of each of the structured metal pads, so as to form atleast three raised structures thereon.
 3. The interconnect component ofclaim 2, wherein said two or more channels are configured so as for saidat least three raised structures to form a 1D or a 2D pattern ofrepeating structures on said each of the structured metal pads.
 4. Theinterconnect component of claim 1, wherein an average width of saidchannels is between 1 and 6 μm, the average width measured in-plane withsaid average plane of said each of the structured metal pads.
 5. Theinterconnect component of claim 1, wherein an average in-plane dimensionof said raised structures is between 4 and 10 μm, the average in-planedimension measured in-plane with said average plane of said each of thestructured metal pads.
 6. The interconnect component of claim 1, whereinan average thickness of said raised structures is between 2 and 6 μm,the average thickness measured perpendicularly to said average plane ofsaid each of the structured metal pads.
 7. The interconnect component ofclaim 6, wherein: an average width of said channels is between 1 and 6μm, the average width measured in-plane with said average plane of saideach of the structured metal pads; an average in-plane dimension of saidraised structures is between 4 and 10 μm, the average in-plane dimensionmeasured in-plane with said average plane of each of the structuredmetal pads; and an average thickness of said raised structures isbetween 2 and 6 μm, the average thickness measured transversely to saidaverage plane of said each of the structured metal pads.
 8. Theinterconnect component of claim 1, wherein the pads are electroplatedmetal pads.
 9. The interconnect component of claim 1, wherein the padsare copper pads.
 10. A set including: a first interconnect component,comprising a first substrate and a set of structured metal pads arrangedon a first main surface of said first substrate, wherein each of thestructured metal pads comprises one or more channels, each extendingin-plane with an average plane of said each of the structured metalpads, so as to form at least two raised structures thereon; and a secondinterconnect component, comprising a second substrate and a set of metalpillars arranged on a second main surface of said second substrate,wherein the pads are adapted for fabricating metal interconnects withrespective metal pillars on the second substrate.
 11. The set of claim10, wherein a first average in-plane dimension of said metal structuredmetal pads is substantially equal to or larger than a second averagein-plane dimension of said metal pillars, wherein the first averagein-plane dimension and the second average in-plane dimension aremeasured in-plane with the first substrate and the second substrate,respectively.
 12. The set of claim 10, wherein the second interconnectcomponent further comprises electronic components in electricalcommunication with at least some of the metal pillars.
 13. The set ofclaim 10, wherein each of the structured metal pads is bonded to arespective, opposite one of the metal pillars, using metal paste, themetal paste sintered so as to form one or more porous metal joint at alevel of said one or more channels, wherein the bonded structured metalpads and opposite metal pillars form metal interconnects between thefirst substrate and the second substrate.
 14. The set of claim 13,wherein the first substrate further comprises redistribution linesformed on or in the first substrate, said redistribution linesconnecting to the metal interconnects at a level of respectivestructured metal pads, so as to form an electrical current path fromeach of the redistribution lines to a respectively connected metalinterconnect, via a respective structured metal pad, in operation, andwherein the one or more channels are arranged so as for said electricalcurrent path to pass through one of said at least two raised structures.15. The set of claim 14, wherein each of the structured metal padscomprises a plurality of channels, each extending in-plane with anaverage plane of each of the structured metal pads, so as to form aplurality of raised structures thereon, the metal paste sintered so asto form a porous metal joint at the level of each of the channels, theplurality of channels arranged so as for said electrical current path topass through one structure within the plurality of raised structures.16. A method for interconnecting two interconnect components, the methodcomprising: providing a first interconnect component, comprising a firstsubstrate and a set of structured metal pads arranged on a first mainsurface of said first substrate, wherein each of the structured metalpads comprises one or more channels, each extending in-plane with anaverage plane of said each of the structured metal pads, so as to format least two raised structures thereon; and providing a secondinterconnect component, comprising a second substrate and a set of metalpillars arranged on a second main surface of said second substrate, andbonding each of the structured metal pads to a respective, opposite oneof the metal pillars, using metal paste, the metal paste sintered so asto form one or more porous metal joint at a level of said one or morechannels, to obtain metal interconnects between the first substrate andthe second substrate, wherein during the bonding, the metal paste issintered by exposing the structured metal pads and metal pillars to areduction agent or one or more reaction products thereof.
 17. The methodof claim 16, wherein said reduction agent comprises a mixture of formicacid vapor and nitrogen.
 18. The method of claim 17, wherein bondingfurther comprises dipping the structured metal pads and metal pillarsinto metal paste prior to applying the structured metal pads torespective, opposite metal pillars.
 19. The method of claim 18, whereinthe structured metal pads are applied with pressure to the respective,opposite metal pillars.
 20. The method of claim 16, wherein providingthe first substrate comprises patterning the structured metal pads toobtain said one or more channels and said at least two raisedstructures.